Synergistic Cu-Sb oxide electrocatalyst synthesized by sol-gel method for high-efficiency nitrate reduction to ammonia with suppressed hydrogen evolution

Antimony is one of the hydrogen evolution poison and copper is one of the well-known catalysts for the nitrate reduction to ammonia (NRA). Therefore, to synthesize an efficient electrode that can have the highest selectivity for the reduction of nitrate to ammonia and is accompanied by the lowest hydrogen evolution, in this study, a combination of different Cu to Sb ratios was prepared on a Ti substrate using the sol-gel method in the form of crystalline oxides (CuSb_yOₓ/Ti) to achieve the best catalytic activity and ammonia yield. A 2:1 ratio of Sb to Cu synthesized and calcined at 600 °C had the best catalytic properties. CuSb_yOₓ/Ti electrocatalysts were evaluated for NRA in an alkaline medium. The CuSb₂O_x electrocatalyst had the highest activity with the lowest cathodic Tafel constant of 78 mV dec^{- 1}. EIS results also showed that CuSb₂O_x has the lowest charge transfer resistance (R_total=3.75 Ω cm²). The measurements revealed that the CuSb₂O_x electrocatalyst performed superlative, with an NH₃ yield of 7280 µg h^{- 1} cm^{- 2} and an F.E. of 89% at a potential of -0.7 V vs. RHE. The high NH₃ yield of this oxide electrocatalyst, compared to other oxide compounds, highlights the synergistic effect of Cu and Sb.